The present invention relates to an economical and high-performance pulse power supply for generating extremely short pulse high voltages to be applied in various kinds of devices utilizing pulse high voltages, including a pulse-energized electrostatic precipitator, a Boxer-Charger for providing charge to dust particles, a pulse-energized ozonizer generating ozone by pulse corona, etc.
The inventor of the present invention succeeded in improving the collection performance of an electrostatic precipitator by proposing with another invention "Pulse-Charging Type Electric Dust Collecting Apparatus" (Japanese Patent Application No. 51-073004 filed on June 21, 1976; U.S. patent application Ser. No. 807240 filed on July 16, 1977; British Pat. No. 1582194 granted on June 15, 1977; German Patent Application No. P-2727858.6-Offenlegungsschrift No. 2727858 dated on Dec. 29, 1977; French Patent Application No. 77-19022 filed on June 21, 1977) a "Pulse-Charging" of an electrostatic precipitator in which a dc high voltage is applied between the discharge and collecting electrodes of the precipitator with a particular construction not described here in detail, and pulse high voltages are applied therebetween on top of the dc high voltage in a superimposed fashion. The inventor of the present invention also succeeded in greatly improving the charging performance of a conventional dust precharging device using dc corona discharge by proposing a novel type of precharger called "Boxer-Charger" with another invention "Device for Electrically Charging Particles" (Japanese Patent Application No. 52-150937 filed on Dec. 5, 1975; U.S. Pat. No. 4,210,949 granted on July 1, 1980; UK Patent GB No. 2012493B granted on Feb. 24, 1982; German Patent Application No. P-2838688.1 filed on Sept. 5, 1978; French Pat. No. 7825125 granted on July 20, 1981) and also another invention "Particle Charging Device (Z)" (Japanese Patent Application No. 54-158852 filed on Dec. 7, 1979). The Boxer Charger of these inventions charges dust particles in an ac charging field by bombardment of monopolar ions from both sides alternately, where the ac charging field is constructed by applying an ac charging voltage across a charging space between the electrode assemblies for producing plane-like plasma ion sources, facing each other at a certain distance and insulated from each other, the said electrode assemblies consisting of a plurarity of corona electrodes for producing plane-like plasma ion source, and the pulse high voltages are applied between the said corona electrodes of each electrode assembly at a certain instant when the said electrode assembly takes a predetermined polarity of the said ac charging voltage to produce corona discharges as the plasma ion sources, and the monopolar ions of the predetermined polarity (e.g. negative polarity) are extracted by the ac charging field to be emitted into the charging space alternately from the electrode assemblies of both sides to traverse back and forth across the said charging space, and thereby to bombard the dust particles entering into the said charging space. The inventor of the present invention further succeeded in improving the performance of an ozonizer by proposing with another invention "Ozone Generating Apparatus" (Japanese Patent Application No. 021878 filed on Feb. 23, 1980) a novel type of an ozonizer which comprises plurarity of discharge electrodes attached on one surface of a solid dielectric plate and an induction electrode attached on the opposite surface of the said dielectric plate, and produces ozone by applying pulse voltages between the discharge and collecting electrodes.
The inventor of the present invention confirmed in all of the above applications that, in order to get the highest performance with the lowest energy consumption, it is necessary to use extremely short pulse high voltages with a pulse duration time of several to several hundreds nanoseconds. The conventional pulse power supply for generating such extremely short pulse high voltages has been the type as illustrated by a circuit diagram of FIG. 1. In this figure, 1 is a dc high voltage source, and its output voltage, V, is supplied via the wires 2, 3 and a current limiting resistance 4 to a pulse forming unit 5 so that it is charged. Here, the pulse forming unit 5 is a capacitive energy storage element for producing the pulse high voltage wave form, such as a high voltage condenser, a high voltage cable, or a L-C delay circuit consisting of a plurarity of inductance elements and condensers in a ladder type connection. 6 is a high speed switching unit; 7 and 8 are connecting wires; 9 is a high voltage coaxial cable transmitting the generated pulse high voltage to the load 12 via the terminals 10 and 11. The high speed switching unit 6 used for generating the said extremely short pulse high voltage is generally a spark switch comprising the electrodes 13 and 14 spaced at a suitable gap distance and contained in a vessel filled with a suitable kind of insulating gas at a suitable pressure. Either a hydrogen thyratron or a high speed thyrister can also be used for the high speed switching unit 6. We take for example a spark switch as the high speed switching unit 6, and assume that its spark voltage, Vs, is set at a value lower than the output voltage of the said dc high voltage source, V, by adjusting the gap distance of the said spark spark switch 6. Then, sparking occurs between the electrodes 13 and 14 at an instant when the voltage across the capacitive energy storage element 5, v, arrived at Vs during its charging process, and the said electrodes are instantaneously short-circuited. The electric charge stored in the element 5 is discharged via the wires 7, 8 and the spark gap 6 through the input impedance (surge impedance) of the high voltage coaxial cable 9 to produce a very fast-rising extremely short pulse high voltage, v.sub.p, at the input of the said cable 9. This pulse voltage proceeds along the cable 9 to the right in a form of a travelling pulse voltage, and applied via the terminals 10 and 12 across the load 12. The spark switch as described above is called "self-triggering type". Whereas the so-called "externally-triggered type" spark switches are also used for the same purpose, such as the spark switch in which its spark voltage, Vs, is set at Vs V and sparking is triggered by applying a particular pulse high voltage between the electrodes 13 and 14 in series to the original gap voltage, V, or the spark switch comprising the third triggering electrode in the gap region between the electrodes 13 and 14 and triggering the spark by applying a triggering pulse high voltage to the said third triggering electrode.
Irrespective of the triggering mechanisms, either self-triggering type or externally-triggering type, the conventional pulse power supply as illustrated in FIG. 1 for generating the extremely short pulse high voltage had the following inherent large disadvantage which greatly reduces the power efficiency of this power supply and produces a large power loss, and thereby makes its use in the various applications as already described almost prohibitive. Namely, in the charging process of the pulse forming unit 5, the full output voltage of the said dc high voltage 1, V, is applied to a series circuit of the current limiting resistance 4 and the pulse forming unit 5, so that the resistance 4 consumes a Joule energy loss in the charging process equal to the energy to be stored in the electrostatic capacity, C, of the pulse forming unit 5, i.e. (1/2)CV.sup.2, and thereby produces a very large energy loss as described above.
The purpose of the present invention is to provide an economical and highly efficient pulse power supply for generating extremely short pulse high voltages by overcoming the above disadvantage.